PROCTER & GAMBLE TO BUY SEARLE UNIT

Although the sale price was withheld, sources put it at $250 million to $300 million. Searle`s over-the-counter products include such brand names as Metamucil, the leading laxative brand; Dramamine, the leading treatment in this country for motion sickness; Icy Hot, a pain-relieving ointment; and other brands marketed outside the United States.

Frederic Greenberg, an analyst at Goldman, Sachs & Co., estimated Searle`s 1985 sales of its over-the-counter drug products at more than $200 million.

The transaction is subject to government antitrust approval, but a P&G spokeswoman said she expected the deal to be closed within 60 days.

Monsanto Co., which acquired Skokie-based Searle in October, had previously announced it planned to sell Searle`s consumer-products businesses and retain the pharmaceuticals unit and the division making NutraSweet, Searle`s brand of aspartame. The St. Louis-based chemicals company plans to use the proceeds to pay off some of the huge debt it assumed in the $2.7 billion deal.

P&G is said to have been a partner of Monsanto`s in the bidding for the entire Searle company when it was for sale earlier this year.

Conspicuously absent from Monday`s announcement was the name of a buyer for the other part of Searle`s consumer-products business, which makes aspartame in tabletop sweetening form under the name Equal.

A Searle spokesman said that P&G`s purchase includes a Phoenix plant that makes Metamucil and packages Equal, but that P&G has agreed to continue making Equal on a contract basis for Searle.

Searle`s overseas pharmaceutical sales force will continue to sell the over-the-counter drugs for a transition period of five years, the Searle spokesman said.

Thomas J. Lipton Inc., which distributes Equal to grocery stores, has been mentioned as a possible buyer of Equal. Other names mentioned include Kellogg Co., which distributes Equal to restaurants, and General Foods Corp.

Analysts estimate that the Equal business will be worth $200 million to $300 million. A buyer would continue to purchase aspartame from Searle, then mix it with stabilizers and package the product. It is unclear whether Searle will sell the overseas rights to the product.

A spokeswoman for Cincinnati-based P&G said the consumer products giant bought the over-the-counter drug business ''because the products enable us to move into new categories of business that are logical extensions of areas we`re already involved in.''

In June, 1982, P&G bought the Norwich pharmaceutical unit of what is now Morton Thiokol Corp. and added such brand names as Pepto-Bismol. In October, P&G agreed to pay $1.2 billion for Richardson-Vicks, whose over-the-counter drugs include cold and cough medications.